Currently, more than 14% of the world’s population is pre-obese or obese. The percentage is even higher in developed countries. Obesity is an important risk factor for a vast number of nonmalignant and malignant digestive diseases. Some of the more important examples are cholelithiasis, nonalcoholic fatty liver disease, and gastroesophageal reflux disease on the one hand and esophageal adenocarcinoma, gastric cardia adenocarcinoma, pancreatic cancer, liver cancer, gallbladder cancer, and colorectal cancer on the other hand. Their epidemic trends as reported in recent studies are reviewed here. Knowledge of their dependencies on obesity will yield a deeper understanding which is necessary to improve prevention and treatment concepts of this epidemic.